A light-regulated, exceptionally active and selective artificial potassium channel

Abstract

Artificial gated ion channels are still rare, particularly when compared to their many ungated counterparts. In this work, we introduce a photoresponsive azobenzene group and an ion-binding crown ether group into a doubly amidated monopeptide scaffold having a capacity to self-assemble into a one-dimensionally aligned, doubly H-bonded columnar structure. While the directionally aligned crown ethers provide the structural basis for transporting K⁺ ions with high selectivity, the similarly aligned azobenzene groups offer the system light modulation, concurrently with surprisingly enhanced ion transport properties with respect to its parent molecule having an octyl side chain. Upon 365 nm UV irradiation to convert trans-azobenzene to its cis-form, the ion transport activity drops drastically by >60% (from 0.98 to 2.60 mol% relative to lipids) in the EC₅₀ value, with fractional ion transport activity-derived K⁺/Na⁺ selectivity substantially decreasing by >70% (from 23.6 to 6.3). The activity and selectivity are fully restored after alternating exposure to visible light at 455 nm.